Rain's stopped play? It's a foregone conclusion (2,7)
I believe the answer is:
no contest
'a foregone conclusion' is the definition.
(both refer to a predictable result)
'rain's stopped play? it's' is the wordplay.
I cannot quite see how this works, but
'play?' could be 'no' (no or noh is a type of Japanese theatre) and 'no' is found within the answer.
'it's' could be 'es' ('e' can mean 'electronic' which is similar to 'IT') and 'es' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for no contest that I've seen before include "Without serious competition -- hands down" , "Winner's obvious" , "The winner is obvious!" , "sure-fire victory" , "one-sided fight?" .)